A nice recommendation from the Twitter blog, Twitsig is a very simple and user friendly tool for creating a graphic of your latest Twitter update. Looks something like this ...
The first commenter on the Twitter blog post says that Twitsig doesn't support UTF-8 though, so no Japanese, Chinese etc. character support.
Here's an alternative developed by Korelab. Looks like it's developed in Japan and does support double byte characters. The design is quite configurable and you can also skip back to older Tweets and refresh.